Swift: Remove from array of strings any element that contains a string from another array-CodePudding

I have array1 and filter it so that any of its elements that contain any of the strings in array2 are removed:

var array1 = ["first.food", "second.easy.good", "third.long.bad", "4.bad.apple", "cinco.Thank You!"]

let array2 = ["food", "bad"]

Desired result: array1 = ["second.easy.good", "cinco.Thank You!"]

I achieve this by looping over array2 and filtering array1,

    for string in array2 {
        array1 = array1.filter { !$0.contains(string) }
    }

result: array1 = ["second.easy.good", "cinco.Thank You!"]

But can it be done in one line? And if so would it be more or less efficient?

edit: removing the word "functionally" from the question based on accepted reply by @matt.

(Previous question: But can it be done functionally in one line? And if so would it be more or less efficient?)

CodePudding user response：

functionally in one line ... efficient?

Efficiency might come from parsing the dot-strings into a Set, and especially from turning the second array into a Set, so that contains is faster; in fact, if they are both sets, you can use intersection, which is insanely efficient.

This would be worth while particularly if the quantities are large, as the preparation does take a little time.

// your premise
let array1 = ["first.food", "second.easy.good", "third.long.bad", "4.bad.apple", "cinco.Thank You!"]
let array2 = ["food", "bad"]

// preparation
let parsedArray1 = array1.map {($0, Set($0.split(separator: ".").map(String.init)))}
let set2 = Set(array2)

// okay, _now_ we can be efficient!
let result = parsedArray1.filter { $0.1.intersection(set2).isEmpty }.map {$0.0}

// done! proof:
print(result) // ["second.easy.good", "cinco.Thank You!"]

But that has nothing to do with "functional programming", which is merely a way of talking, not a way of improving efficiency. Nor is the "number of lines" of the slightest relevance to efficiency; a one-liner (like my let result line) is fun to look at, but it has no effect whatever on what goes on behind the scenes.